Model-Based Spectrum Management

Transcription

1 Model-Based Spectrum Management Making Spectrum Management Agile and Enabling Dynamic Spectrum Access (DSA) John A. Stine November 2011.

2 Purpose Familiarize you with Spectrum consumption modeling Using models to improve spectrum management Using models to convey DSA policy Inspire you To want to learn more about Model-Based Spectrum Management (MBSM) To download and review the MBSM Modeling Manual To contribute to making it better To assist in making it a standard Page 2

3 The Vision Spectrum consumption modeling becomes the core of a very dynamic spectrum management capability serving as a loose coupler among spectrum management (SM) systems and radio frequency (RF) systems and devices Enables Innovation #6 of the 10 Most Wanted Wireless Innovations: Flexible Regulatory Framework for Temporary, Cooperative and Opportunistic Access Page 3

4 What is a loose coupler? Layer Innovation Layer Interface Layer Bowtie Diversity Loose Coupler Diversity Layer Innovation A thing that exists at the intersection of a large set of systems that allow them to interoperate and to be integrated A key component of innovation and composable capabilities Layers enable local innovation Loose couplers enable integration Bowties enable composability Page 4

5 Well known examples of loose coupling Power Users Innovation Applications Composability 60 Hz AC Standard IP Composability Power Producers Benefits Integration Interoperability Innovation Innovation Datalink Technologies Page 5

6 Spectrum Consumption Modeling as a Loose Coupler Network Operations and Spectrum Management Innovation Spectrum Management Diversity Channel configuration DSA policy Spectrum use (loose coupler) SCM Standardization Spectrum Use Diversity RF Coexistence and Dynamic Spectrum Access Innovation Page 6

7 What is the problem with current approaches? RF system characteristics What constitutes interference How the systems will be used Tool 1 Models of terrain and propagation Channel Assignments The output is a decision Knowledge is created in the planning process but not captured in the output Channel assignments do not convey the consumption of spectrum or what constitutes compatible reuse. Consumption and compatibility is based on the analysis methods embedded in tools and the judgment of the spectrum manager Managers must study the problem but the thought processes of the study are lost in the output Analysis methods vary from tool to tool and understanding of intent and judgment vary from manager to manager. Page 7

8 Why is this a problem? RF system characteristics What constitutes interference Must know the RF system characteristics and what constitutes interference How the systems will be used Tool 1 Tool 2 Models of terrain and propagation Output is just a decision Channel Assignments Models of terrain and propagation Knowledge is created in the planning process but not captured in the output Must know how the system is being used To determine the effect of a channel assignment, spectrum managers must know the intent of the spectrum user and the judgment of the managers that made the decisions. A hard problem that results in managers seeking persistent solutions Page 8

9 How MBSM is different RF system characteristics What constitutes interference Knowledge in the model Tool 1 Tool 2 How the systems will be used Models of terrain and propagation Spectrum Consumption Model Models of terrain and propagation The Spectrum Consumption Model contains the intent of the user and the judgment of the spectrum manager. It is complemented with a specified approach to compute compatibility Spectrum Consumption Models convey the consumption of spectrum and what constitutes compatible reuse Page 9

10 Why add modeling? Captures and allows sharing of judgment and intent Enables distribution of the spectrum management problem Changes nature of spectrum management From seeking persistent solutions to one seeking dynamic solutions Greater spatial and temporal resolution Enables creation of algorithms for improved spectrum management Assessing compatibility of uses Automation of channel assignment Searching for suitable spectrum Supports Dynamic Spectrum Access Models are policy Models are machine readable Provides means to manage DSA systems Conceals sensitive details of equipment and its use while still revealing spectrum consumption for spectrum management tasks Page 10

11 Proposed modeling constructs Maximum power density Spectrum mask Underlay mask Power map Propagation map Intermodulation masks Platform Location Start time End time Minimum power density Protocol or policy Enable greater resolution in spectrum management Can capture unique characteristics of spread spectrum systems Can capture antenna effects Can capture environmental effects Captures susceptibility to intermodulation Can capture behaviors that enable compatible reuse Not data about a system but used to build a model of spectrum use Models are information! Page 11

12 Combining constructs into models Constructs define emissions Constructs define interference Modeling constructs are found in transmitter and receiver models and in system and collection headings Transmitter Receiver System Transmitter_1 Transmitter_2 Transmitter_n Recevier_1 Receiver_2 Receiver_m End of System Collection System_1 System_2 System_i Transmitter_1 Transmitter_2 Transmitter_j Recevier_1 Receiver_2 Receiver_k End of Collection Proposal provides an XML schema for this type of model construction Page 12

13 Model and collection function System Model Constructs in heading define the boundaries of system operation Lists transmitter and receiver models with more limiting constructs Collective Consumption Listing Constructs in heading define the limits to which the collection is complete Lists systems, transmitters and receivers of spectrum consumers that consume spectrum within the limits of the collection Spectrum Authorization Listings Constructs in the heading define the limits of the overall authorization The lists of system, transmitter, and receiver models identify available spectrum Spectrum Constraint Listings Constructs in the heading define the limits of the collection of constraints The lists of system, transmitter, and receiver models identify existing uses of spectrum that have precedence Page 13

14 Dynamic spectrum management Build systems that exploit modeling Network Operations and Spectrum Management Spectrum Management Diversity (loose coupler) SCM Spectrum Use Diversity RF Coexistence and Dynamic Spectrum Access 1. Request spectrum 2. Spectrum manager (SM) sends authorization listing 3. Mission planner creates plan and the necessary spectrum consumption models (SCM) 4. Mission level SCM sent to the SM as a request 5. Mission level spectrum use granted 6. SM identifies reuse opportunities 7. Potential users of spectrum notified of opportunities with a collective listing 8. Network manager (NM) identifies reuse and requests spectrum using a SCM 9. SM reviews NM s request and authorizes use 10.NM informs cognitive radios of policy using SCM Page 14

15 Conveying Policy to DSA Systems End-to-end direct authorization Spectrum Management System Dynamic Spectrum Access System Database of active models Spectrum Manager 1 Systems Manager Direct Authorization A collection of models that define spectrum that may be used End-to-end dynamic authorization Spectrum Management System Dynamic Spectrum Access System Database of active models Spectrum Manager 2 Systems Manager Dynamic Authorization A collection of two types of models: 1. Models that define in general spectrum that may be used 2. Models that constrain that use Hybrid authorization Spectrum Management System Dynamic Spectrum Access System Database of active models Spectrum Manager 2 Systems Manager Page 15

16 Dynamic Authorization Example of a primary system with a single transmitter and a single receiver This transmitter would interfere These transmitters will not interfere This receiver cannot hear In natural language or as a nested if-then-else statement how would you write the policy? This receiver can receive Page 16

17 Dynamic Authorization - 2 Modeling the transmitter and receiver pair Model Constructs Components used to model a simplex radio link System Heading Transmitter Receiver Maximum Power Density R R Spectrum Mask R Underlay Mask R Propagation Map R R Power Map R R Intermodulation Mask O O Platform Name O O Location R - Point R - Point Start Time R End Time R Minimum Power Density Protocol or Policy O R - Required, O - Optional, T - Typical (To provide a refined definition) Spectrum consumption models are policy! Page 17

18 Protocol or Policy- 1 Rationale Enables finer resolution sharing through behaviors at components Means to specify how spectrum sensing may be used to inform spectrum use decisions Means to exploit reuse opportunities that come from knowing the specific behaviors of incumbents Protocols specify specific access mechanisms while policies specify conditions for use policy driven systems can choose their own access mechanism among themselves Data Structure Name plus parameters Units Units of parameter values are specified as part of the named protocol or policy definition Dependencies Apply to spectrum in the larger model DSA systems must be rated for the different policies and protocols to use them Page 18

19 A protocol example The scenario Multiple co-located MANETs with one a primary user Goal is to ensure primary users get precedence and secondary users can use whatever spectrum the primary users do not use Page 19

20 A protocol that enables sharing Synchronous Collision Resolution (SCR) a slotted protocol using signaling to arbitrate access P E Broadcast Data 1 Data 2 Data 3... SM Priority Phase EI CR Signaling Transmission Slot 20

21 A protocol that enables sharing Differentiating primary and secondary use P E Broadcast Data 1 Data 2 Data 3... SM Priority Phase EI

22 The Result The primary always get precedence in access Secondary users can fill in the spaces around the primary user Page 22

23 Specifying the Protocol Name Parameters <SCR PS, 0.05, 0.035, 2> Signal Slot Size Transmission Slot Duration Signal Duration Page 23

24 Policy Example A policy is a generalized behavior with no restriction on the protocols used by the system for arbitrating its own access Simple sensing Sense the channel for a particular power threshold, p th A duration of non-use indicates availability, t f A sensing period for verifying availability, t s An abandonment time, t a Policy Description Simple_Sensing, pth, t f, ts, ta Page 24

25 What we want you to do Support the development of a spectrum consumption modeling standard and consider its use for spectrum use databases and for specifying DSA policy Network Operations and Spectrum Management Spectrum Management Diversity (loose coupler) SCM Spectrum Use Diversity RF Coexistence and Dynamic Spectrum Access The Modeling and Computation Manual is a first attempt to create a standard and is available at Page 25

26 Conclusion Model-Based Spectrum Management has the potential to greatly improve spectrum management and to liberalize access to spectrum MBSM enables the management of DSA systems MITRE has made a first attempt to create a standard for modeling which we want you to review and try to make better You can join our collaboration workspace by sending me a request jstine@mitre.org Page 26

27 Backup Page 27

28 General process of computing compatibility Determine if uses will overlap in time and spectrum Determine the constraining points (the point of primary operation and the point of secondary operation that most restrict the secondary user) Constraining primary receiver Constraining secondary transmitter Secondary mobile user Primary broadcast user Compute the allowed transmit power of the secondary user Page 28

29 Determining compatible reuse Signal to interference margin, PM underlay 0 50 PM masks = 0dB Power in db scale PM r_prop (d 1 ) Bound on the transmitter power Attenuation from the transmitter to the constraining point Allowed secondary power density at 1 meter in the constraining point direction PM prop (d 2 ) Attenuation from the secondary transmitter to the constraining point Distance to the constraining point Primary transmitter log(d 1 ) Constraining point log(d 2 ) Secondary transmitter 29

30 Value of Modeling an Example 100 km 50 km 5 hrs 100 km As an example, imagine modeling the spectrum consumption of a UAV that flies along the path shown above Page 30

31 Value of Modeling an Example Radius = 200 km 5 hrs Without a model, a secondary user does not have complete knowledge of the UAV s use To avoid interference, secondary user assumes UAV s location may be anywhere within a larger area that fully captures the actual path Page 31

32 Value of Modeling an Example Each cylinder: 10 km radius 20 min Total time = 5 hrs By using a finer model, the path can be covered by a series of smaller cylinders, each covering 20 minutes of the route Page 32

33 Value of Modeling an Example To determine consumption, we must integrate over time, space, and spectrum The volume of the region that experiences interference changes depending on the frequency Page 33

34 Value of Modeling an Example Computing the consumptions of both models, we can see that the total consumption of the refined model is ~1/3 that of the coarse model Page 34

35 Key differences in future tools Today Data Tools Judgment Decision The judgment of the spectrum manager is lost after the decision is made The judgment of the spectrum manager and the intent of the user is embedded in the model Proposed Data Judgment & Intent Tools Models Tools Decision The models enable algorithms to perform hard spectrum management tasks Page 35